1. Field of the Invention
The present invention relates to recording and accessing metadata relating to recorded material. The present invention also relates to using the recorded metadata to access further metadata.
2. Description of the Prior Art
In embodiments of the present invention, the recorded material comprises video and may also comprise audio information. Metadata is data relating to the recorded information.
In embodiments of the present invention, the recorded material comprises video information, and may also comprise audio information. In the embodiments of the present invention metadata is information related to the recorded video information (and the audio information if provided). The following refers to video information by way of example, and for clarity, but in its broadest aspects the ideas of the invention may be applied to other data.
When a video sequence is recorded it is essential to at least identify the data carrier, such as tape or disc, on which it is recorded. Conventionally the sequence is identified on a physical label attached to the carrier. It is also desirable to record such data on the carrier with the video sequence. The recorded data is one example of metadata. However, it is naturally desirable to maximise the video information recorded so as to aid video production operations. The video information is recorded on tape in helical scan tracks. Linear control and time code tracks are also provided on the tape. Also audio information, and control information such as time codes are typically recorded in the helical tracking. A linear audio cue track may also be provided on the tape [1]. Consequently, there are problems of: how or where to record metadata; and what metadata to record on a data carrier so as to provide useful information but at the same time to minimise the information recorded.
One way of identifying material recorded on a data carrier or recording medium is to use a UMID which is a Unique Material Identifier. A basic UMID has 32 bytes; an extended UMID has 64 bytes. The paper “Essence & Metadata Linking via the umid” IEE NBSS 6 July 1999 by J. H. Wilkinson, Sony B.P.E, UK. describes the SMPTE UMID and describes how a UMID carried with the “Essence” i.e. raw picture/audio information, may be used to link that Essence to other metadata stored in a computer storage system. The UMID may be carried in the VBI (Vertical Blanking Internal) of the video, or embedded in user bits of an AES 3 Audio Channel, if such an Audio channel is provided.
Using the VBI or the AES 3 audio channel for the recording of metadata, reduces the space available on a carrier, e.g. a disc or tape, to record the video or audio information on for audio. If the video is MPEG and the VBI data is stored in the Video-Elementary Stream (V-ES) it may reduce the space available for the compressed video bitstream.
At present, tape is the predominant medium for recording video. There are a variety of tape formats used in video production. It is desirable to record metadata on a tape in such a way that it can be recorded on as large a variety of tape formats as possible and preferably on any existing tape format. It is also desirable to store a large body of metadata relating to material recorded on a tape. It is also desirable to record metadata relating to material recorded on other forms of recording media, especially discs.
According to one aspect of the present invention there is provided a method of recording information relating to a sequence of data fields, each of which fields has associated therewith a code identifying the said field, the code having bits which identify the fields and user bits which are definable by a user, in which method bits of additional data relating to the said sequence, and comprising a number of bits greater than the number of user bits in a single field identifying code, are allocated to user bits of a plurality of field identifying codes of the said sequence.
Most preferably, the data fields are video fields and the codes are time codes. The data is preferably recorded on a medium such as tape or disc. Preferred embodiments of the invention concern tapes. Putting the additional data into the user bits of the time codes, allows the data to be recorded in any known tape format, it being believed that all known tape formats have time codes with user bits. In a most preferred embodiment of the invention, the said additional data which is recorded in the time codes is a medium identifier which distinguishes the example of the medium e.g. tape, disc or other recording medium from other examples thereof.